Desperately trying to shed the pounds? You are far more likely to success if you diet and exercise with a friend.

The average female will shed more than 10 pounds when she has girlfriends who are willing to eat healthily and train with her. But a fifth of those who choose to go it alone don't drop a single pound.

The study of 3,000 women also revealed 61 per cent find it almost impossible to summon up the energy to exercise alone. However the same proportion enjoy going for a jog or taking a swim with a friend - and admit they push themselves harder if they have company.

Exercising together has the added benefit of bringing you closer to a friend - more than half of those surveyed thought working out with a mate had improved their relationship.

Sian Lewis, director of female car insurance company Diamond which commissioned the survey, said: 'It can be really hard to find the time, energy and enthusiasm for exercising when there's no-one to do it with.

'At the end of a long busy day at work, it would be so easy to slip into the arm chair for a few hours to relax, rather than go out for a jog or swim.

'But having a friend who is interested in keeping fit and toned can really help keep motivation - suddenly exercise isn't just about getting sweaty, and losing weight, it's about catching up on the latest gossip, and having a bit of quality time together.'

Seven out of ten girls said exercise was less of a chore when they did it with friends, but over half admitted talking non-stop during the work-out.

But the poll shows dieting and exercising with a friend isn't all about improving relationships - for some it's a fashion contest.

A third of girls always buy themselves a new exercise outfit to train with a friend for the first time. The same proportion always wear make up when exercising.

Sian Lewis added: 'Women wouldn't be women if they didn't pay some attention to their appearance before exercising with a friend.

'Girls like to look their best at all times, whether it's in the gym, in the pub or at work, and there's no reason why we can't combine a bit of fitness with a bit of glamour - who knows who you might bump into.'